Re: [time-nuts] theoretical Allan Variance question

[Tom Van Baak]

> One might expect that the actual ADEV value in this situation would be
> exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
> be surprising. My actual measured value is about 0.65 ns, which does not
> seem to have an obvious explanation.  This brings to mind various questions:
> 
> What is the theoretical ADEV value of a perfect time-interval measurement
> quantized at 1 ns? What's the effect of an imperfect measurement
> (instrument errors)? Can one use this technique in reverse to sort
> instruments by their error contributions, or to tune up an instrument
> calibration?

Hi Stu,

If you have white phase noise with standard deviation of 1 then the ADEV will 
be sqrt(3). This is because each term in the ADEV formula is based on the 
addition/subtraction of 3 phase samples. And the variance of normally 
distributed random variables is the sum of the variances. So if your standard 
deviation is 0.5 ns, then the AVAR should be 1.5 ns and the ADEV should be 0.87 
ns, which is sqrt(3)/2 ns. You can check this with a quick simulation [1].

Note this assumes that 1 ns quantization error has a normal distribution with 
standard deviation of +/- 0.5 ns. Someone who's actually measured the hp 5334B 
quantization noise can correct this assumption.

/tvb

[1] Simulation:

C:\tvb> rand 10 0.5e-9 0 | adev4 /at 1
rand 10(count) 5e-010(sdev) 0(mean)
** tau from 1 to 1 step 1
   1 a 8.676237e-010 8 t 5.009227e-010 8

In this 100k sample simulation we see ADEV is close to sqrt(3)/2 ns. The TDEV 
is 0.5 ns. This is because TDEV is based on tau * MDEV / sqrt(3). In other 
words, the sqrt(3) is eliminated in definition of TDEV.


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Re: [time-nuts] our favorite topics

[Gerhard Hoffmann]

Am 30.10.2016 um 01:56 schrieb KA2WEU--- via time-nuts:

The Parzen book was on my list (Amazon ), I find these books,  including
Rhea's book practically useless as they do not provide the necessary  non
-linear noise analysis, and do not have real live examples with test data.
Cerda's "Understanding Quartz Crystals and Oscillators book I have not  seen.
  
73 de Ulrich
I really do not like to see Rhea dissed this way. Yes, nonlinear sim may 
buy another dB or two,
but in the end one has to stay at least somewhat linear, lest one builds 
an 1/f upconverter.

(and Harbec does nonlinear.)

Others don't even have their linear basics complete; everybody talks 
loop gain but
nobody shows how you get from your network analyzer to the correct 
answer of a
circuit whose output is terminated with its own input and whose input is 
terminated

with its own output. It took Rhea to present that on page 3 or so.

And I see a lot of examples compared to actual measurements, and the
Genesys design kits simply work. In fact, Rhea's Genesys is the one 
simulator that

saved me most of the time, and that includes LTspice, which says a lot.

He more or less forced Agilent to buy a competitor from the market, while
they had their own ADS. (which tries to be everybody's darling, nothing it
can't do, but it is too complicated if you do not use it every day.)



I found Frerking's "Crystal Oscillator Design and  Temperature

Compensation"

to be a fruitful read. It's free on the  archive,
  

https://archive.org/details/CrystalOscillatorDesignTemperatureCompensation  .


Silly me, I've bought it. But his book on digital radio is much better.


vy 73 de Gerhard, DK4XP
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Re: [time-nuts] theoretical Allan Variance question

[Michael Wouters]

Dear Stewart

FWIW, if you do the experiment I suggested (TI measurement on
identical 10 MHZ etc) on a HP53132A counter, you get ADEV = 2.0x10^-10
at 1 second.

The manual says the LSD is 150 ps; when you include trigger errors, it
specifies a resolution of 300 ps. The 200 ps implied by the
measurement above is somewhere in between. The specs may be
conservative though.

As Bob Camp said, in Situation 2, you see the noise of the measurement system.

Cheers
Michael

On Sun, Oct 30, 2016 at 1:17 PM, Bob Camp  wrote:
> Hi
>
> Well, situation one:
>
> You have two perfect sources.
> Your measuring device is noiseless
> If your devices are in perfect sync, you get a series of zeros
> Your ADEV is zero
>
> Situation two:
>
> Same sources
> Noisy measuring device
> You get the standard deviation of the difference in measurements
> Your ADEV is simply a measure of the noise of the measuring device
>
> Situation three:
>
> Your sources are much worse than 1x10^-9 at 1 second
> Your ADEV is the proper number for your sources (or close to it)
>
> Situation four:
>
> The real world, you have a bit of each and you really don’t know
> what is what.
>
> Lots of possibilities and no single answer.
>
> Bob
>
>> On Oct 29, 2016, at 7:38 PM, Stewart Cobb  wrote:
>>
>> What's the expected value of ADEV at tau = 1 s for time-interval
>> measurements quantized at 1 ns?
>>
>> This question can probably be answered from pure theory (by someone more
>> mathematical than me), but it arises from a very practical situation. I
>> have several HP5334B counters comparing PPS pulses from various devices.
>> The HP5334B readout is quantized at 1 ns, and the spec sheet (IIRC) also
>> gives the instrument accuracy as 1 ns.
>>
>> The devices under test are relatively stable. Their PPS pulses are all
>> within a few microseconds of each other but uncorrelated.  They are stable
>> enough that the dominant error source on the ADEV plot out to several
>> hundred seconds is the 1 ns quantization of the counter. The plots all
>> start near 1 ns and follow a -1 slope down to the point where the
>> individual device characteristics start to dominate the counter
>> quantization error.
>>
>> One might expect that the actual ADEV value in this situation would be
>> exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
>> be surprising. My actual measured value is about 0.65 ns, which does not
>> seem to have an obvious explanation.  This brings to mind various questions:
>>
>> What is the theoretical ADEV value of a perfect time-interval measurement
>> quantized at 1 ns? What's the effect of an imperfect measurement
>> (instrument errors)? Can one use this technique in reverse to sort
>> instruments by their error contributions, or to tune up an instrument
>> calibration?
>>
>> I'd be grateful for answers to any of these questions.
>>
>> BTW, thanks to whichever time-nuts recommended the HP5334B, back in the
>> archives; they're perfect for what I'm doing. And thanks to fellow time-nut
>> Rick Karlquist for his part in designing them.
>>
>> Cheers!
>> --Stu
>> ___
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>> and follow the instructions there.
>
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Re: [time-nuts] theoretical Allan Variance question

[Bob Camp]

Hi

Well, situation one:

You have two perfect sources.
Your measuring device is noiseless 
If your devices are in perfect sync, you get a series of zeros
Your ADEV is zero

Situation two:

Same sources
Noisy measuring device
You get the standard deviation of the difference in measurements
Your ADEV is simply a measure of the noise of the measuring device

Situation three:

Your sources are much worse than 1x10^-9 at 1 second
Your ADEV is the proper number for your sources (or close to it)

Situation four:

The real world, you have a bit of each and you really don’t know 
what is what.

Lots of possibilities and no single answer.

Bob

> On Oct 29, 2016, at 7:38 PM, Stewart Cobb  wrote:
> 
> What's the expected value of ADEV at tau = 1 s for time-interval
> measurements quantized at 1 ns?
> 
> This question can probably be answered from pure theory (by someone more
> mathematical than me), but it arises from a very practical situation. I
> have several HP5334B counters comparing PPS pulses from various devices.
> The HP5334B readout is quantized at 1 ns, and the spec sheet (IIRC) also
> gives the instrument accuracy as 1 ns.
> 
> The devices under test are relatively stable. Their PPS pulses are all
> within a few microseconds of each other but uncorrelated.  They are stable
> enough that the dominant error source on the ADEV plot out to several
> hundred seconds is the 1 ns quantization of the counter. The plots all
> start near 1 ns and follow a -1 slope down to the point where the
> individual device characteristics start to dominate the counter
> quantization error.
> 
> One might expect that the actual ADEV value in this situation would be
> exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
> be surprising. My actual measured value is about 0.65 ns, which does not
> seem to have an obvious explanation.  This brings to mind various questions:
> 
> What is the theoretical ADEV value of a perfect time-interval measurement
> quantized at 1 ns? What's the effect of an imperfect measurement
> (instrument errors)? Can one use this technique in reverse to sort
> instruments by their error contributions, or to tune up an instrument
> calibration?
> 
> I'd be grateful for answers to any of these questions.
> 
> BTW, thanks to whichever time-nuts recommended the HP5334B, back in the
> archives; they're perfect for what I'm doing. And thanks to fellow time-nut
> Rick Karlquist for his part in designing them.
> 
> Cheers!
> --Stu
> ___
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Re: [time-nuts] theoretical Allan Variance question

[Michael Wouters]

Dear Stuart

In a perfect world, your TI measurements would have a uniform
probability distribution function with amplitude 0.5 ns and mean value
0 ns. At least, this is the kind of PDF you would assume for
"resolution error". For this distribution, ADEV is 0.5 ns.

I don't know the HP5334B, perhaps its effective resolution is a bit
poorer than 0.5 ns, which I assume is the displayed resolution ?

BTW, one way to remove instability of the DUTs from this kind of test
is to reference the counter to 5/10 MHz and then do your TI
measurement with the same 5/10 MHz input to each channel of the
counter.

Cheers
Michael

On Sun, Oct 30, 2016 at 10:38 AM, Stewart Cobb  wrote:
> What's the expected value of ADEV at tau = 1 s for time-interval
> measurements quantized at 1 ns?
>
> This question can probably be answered from pure theory (by someone more
> mathematical than me), but it arises from a very practical situation. I
> have several HP5334B counters comparing PPS pulses from various devices.
> The HP5334B readout is quantized at 1 ns, and the spec sheet (IIRC) also
> gives the instrument accuracy as 1 ns.
>
> The devices under test are relatively stable. Their PPS pulses are all
> within a few microseconds of each other but uncorrelated.  They are stable
> enough that the dominant error source on the ADEV plot out to several
> hundred seconds is the 1 ns quantization of the counter. The plots all
> start near 1 ns and follow a -1 slope down to the point where the
> individual device characteristics start to dominate the counter
> quantization error.
>
> One might expect that the actual ADEV value in this situation would be
> exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
> be surprising. My actual measured value is about 0.65 ns, which does not
> seem to have an obvious explanation.  This brings to mind various questions:
>
> What is the theoretical ADEV value of a perfect time-interval measurement
> quantized at 1 ns? What's the effect of an imperfect measurement
> (instrument errors)? Can one use this technique in reverse to sort
> instruments by their error contributions, or to tune up an instrument
> calibration?
>
> I'd be grateful for answers to any of these questions.
>
> BTW, thanks to whichever time-nuts recommended the HP5334B, back in the
> archives; they're perfect for what I'm doing. And thanks to fellow time-nut
> Rick Karlquist for his part in designing them.
>
> Cheers!
> --Stu
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] our favorite topics

[Peter Reilley]

Please don't take this wrong but your use of the word "treaty" is wrong.
I think you mean "treatise".

Pete.

On 10/29/2016 8:05 PM, Attila Kinali wrote:

Hoi Ulrich,

On Sat, 29 Oct 2016 19:56:53 -0400
KA2WEU--- via time-nuts  wrote:


The Parzen book was on my list (Amazon ), I find these books,  including
Rhea's book practically useless as they do not provide the necessary  non
-linear noise analysis, and do not have real live examples with test data.
Cerda's "Understanding Quartz Crystals and Oscillators book I have not  seen.

You don't have to look then. There are very few people who actually looked
at the noise in oscillator circuits and tried to optimize it. You and
Poddar are definitely those who wrote most about it. Then comes probably
Enrico. One can find a paper here and there analysing different noise
sources, but never a complete treaty.

The lack of noise/non-linear analysis does not mean you cannot learn
from those books, though. They are good books to learn from on how to
build an oscillator. Once that is achieved, one can learn how to make
it low noise by reading your books :-)

Attila Kinali



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Re: [time-nuts] theoretical Allan Variance question

[Bob Stewart]

Perfect?  I can't tell you that.  But I can tell you that the 1s ADEV that I 
can measure is limited to the stability of the reference oscillator, and to the 
resolution and stability of the measuring device.  For example, I have an HP 
5370A TIC.  It's good to about +/- 20ps.  So, that's the lower limit on the 1s 
ADEVs that I can measure.
Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Stewart Cobb 
 To: time-nuts@febo.com 
 Sent: Saturday, October 29, 2016 6:38 PM
 Subject: [time-nuts] theoretical Allan Variance question
   
What's the expected value of ADEV at tau = 1 s for time-interval
measurements quantized at 1 ns?

This question can probably be answered from pure theory (by someone more
mathematical than me), but it arises from a very practical situation. I
have several HP5334B counters comparing PPS pulses from various devices.
The HP5334B readout is quantized at 1 ns, and the spec sheet (IIRC) also
gives the instrument accuracy as 1 ns.

The devices under test are relatively stable. Their PPS pulses are all
within a few microseconds of each other but uncorrelated.  They are stable
enough that the dominant error source on the ADEV plot out to several
hundred seconds is the 1 ns quantization of the counter. The plots all
start near 1 ns and follow a -1 slope down to the point where the
individual device characteristics start to dominate the counter
quantization error.

One might expect that the actual ADEV value in this situation would be
exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
be surprising. My actual measured value is about 0.65 ns, which does not
seem to have an obvious explanation.  This brings to mind various questions:

What is the theoretical ADEV value of a perfect time-interval measurement
quantized at 1 ns? What's the effect of an imperfect measurement
(instrument errors)? Can one use this technique in reverse to sort
instruments by their error contributions, or to tune up an instrument
calibration?

I'd be grateful for answers to any of these questions.

BTW, thanks to whichever time-nuts recommended the HP5334B, back in the
archives; they're perfect for what I'm doing. And thanks to fellow time-nut
Rick Karlquist for his part in designing them.

Cheers!
--Stu
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Re: [time-nuts] our favorite topics

[Attila Kinali]

Hoi Ulrich,

On Sat, 29 Oct 2016 19:56:53 -0400
KA2WEU--- via time-nuts  wrote:

> The Parzen book was on my list (Amazon ), I find these books,  including 
> Rhea's book practically useless as they do not provide the necessary  non 
> -linear noise analysis, and do not have real live examples with test data.  
> Cerda's "Understanding Quartz Crystals and Oscillators book I have not  seen.

You don't have to look then. There are very few people who actually looked
at the noise in oscillator circuits and tried to optimize it. You and
Poddar are definitely those who wrote most about it. Then comes probably
Enrico. One can find a paper here and there analysing different noise
sources, but never a complete treaty.

The lack of noise/non-linear analysis does not mean you cannot learn
from those books, though. They are good books to learn from on how to
build an oscillator. Once that is achieved, one can learn how to make
it low noise by reading your books :-)

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] our favorite topics

[KA2WEU--- via time-nuts]

The Parzen book was on my list (Amazon ), I find these books,  including 
Rhea's book practically useless as they do not provide the necessary  non 
-linear noise analysis, and do not have real live examples with test data.  
Cerda's "Understanding Quartz Crystals and Oscillators book I have not  seen.
 
73 de Ulrich 
 
 
 
 
In a message dated 10/29/2016 7:32:46 P.M. Eastern Daylight Time,  
att...@kinali.ch writes:

On Sat,  29 Oct 2016 15:38:33 -0400
Scott Stobbe   wrote:

> I found Frerking's "Crystal Oscillator Design and  Temperature 
Compensation"
> to be a fruitful read. It's free on the  archive,
>  
https://archive.org/details/CrystalOscillatorDesignTemperatureCompensation  .
> 
> Are there any recommendations for one or more book(s) that  are definitely
> worth skimming through, or reading?

Depends for  what. If you are looking for books on crystal oscillators
and how to build  them, I would recommend Parzen's book "Design of
Crystal and Other Harmonic  Oscillators". It's probably the most complete
treaty I have seen (though i  have not completely read it). Rhea's last
book "Discrete Oscillator Design"  is definetly also worth a look and
easier written than Parzen's book, but  much less complete. Another book
worth considering, though a bit expensiv  IMHO, is Cerda's "Understanding
Quartz Crystals and Oscillators". Another  current book is Everard's
"Fundamentals of RF Circuit Design: with Low  Noise Oscillators".
If you are interested in harmonic oscillators in  general, then a look
at Ulrich's and Poddar's book "The Design of Modern  Microwave Oscillators
for Wireless Applications" is definitely worth a  look. Quite a bit of
it is also applicable to quartz oscillators and it  contains together with
"A New and Efficient Method of Designing Low Noise  Microwave  Oscillators"
(http://synergymwave.com/Articles/a-new-efficient-method-of-designing-low-no
ise-microwave-oscillators.pdf)  the most on how to get oscillator noise
down.


If you have a IEEE  account, you can get the older of these books
(and a few othersothers) from  the UFFC website:  
http://www.ieee-uffc.org/publications/books/index.asp


Attila Kinali

-- 
Malek's  Law:
Any simple idea will be worded in the most  complicated  way.
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[time-nuts] theoretical Allan Variance question

[Stewart Cobb]

What's the expected value of ADEV at tau = 1 s for time-interval
measurements quantized at 1 ns?

This question can probably be answered from pure theory (by someone more
mathematical than me), but it arises from a very practical situation. I
have several HP5334B counters comparing PPS pulses from various devices.
The HP5334B readout is quantized at 1 ns, and the spec sheet (IIRC) also
gives the instrument accuracy as 1 ns.

The devices under test are relatively stable. Their PPS pulses are all
within a few microseconds of each other but uncorrelated.  They are stable
enough that the dominant error source on the ADEV plot out to several
hundred seconds is the 1 ns quantization of the counter. The plots all
start near 1 ns and follow a -1 slope down to the point where the
individual device characteristics start to dominate the counter
quantization error.

One might expect that the actual ADEV value in this situation would be
exactly 1 ns at tau = 1 second.  Values of 0.5 ns or sqrt(2)/2 ns might not
be surprising. My actual measured value is about 0.65 ns, which does not
seem to have an obvious explanation.  This brings to mind various questions:

What is the theoretical ADEV value of a perfect time-interval measurement
quantized at 1 ns? What's the effect of an imperfect measurement
(instrument errors)? Can one use this technique in reverse to sort
instruments by their error contributions, or to tune up an instrument
calibration?

I'd be grateful for answers to any of these questions.

BTW, thanks to whichever time-nuts recommended the HP5334B, back in the
archives; they're perfect for what I'm doing. And thanks to fellow time-nut
Rick Karlquist for his part in designing them.

Cheers!
--Stu
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Re: [time-nuts] our favorite topics

[Attila Kinali]

On Sat, 29 Oct 2016 15:38:33 -0400
Scott Stobbe  wrote:

> I found Frerking's "Crystal Oscillator Design and Temperature Compensation"
> to be a fruitful read. It's free on the archive,
> https://archive.org/details/CrystalOscillatorDesignTemperatureCompensation .
> 
> Are there any recommendations for one or more book(s) that are definitely
> worth skimming through, or reading?

Depends for what. If you are looking for books on crystal oscillators
and how to build them, I would recommend Parzen's book "Design of
Crystal and Other Harmonic Oscillators". It's probably the most complete
treaty I have seen (though i have not completely read it). Rhea's last
book "Discrete Oscillator Design" is definetly also worth a look and
easier written than Parzen's book, but much less complete. Another book
worth considering, though a bit expensiv IMHO, is Cerda's "Understanding
Quartz Crystals and Oscillators". Another current book is Everard's
"Fundamentals of RF Circuit Design: with Low Noise Oscillators".
If you are interested in harmonic oscillators in general, then a look
at Ulrich's and Poddar's book "The Design of Modern Microwave Oscillators
for Wireless Applications" is definitely worth a look. Quite a bit of
it is also applicable to quartz oscillators and it contains together with
"A New and Efficient Method of Designing Low Noise Microwave Oscillators"
(http://synergymwave.com/Articles/a-new-efficient-method-of-designing-low-noise-microwave-oscillators.pdf)
 the most on how to get oscillator noise
down.


If you have a IEEE account, you can get the older of these books
(and a few othersothers) from the UFFC website: 
http://www.ieee-uffc.org/publications/books/index.asp


Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] our favorite topics

[KA2WEU--- via time-nuts]

On what topic ? older book miss the phase noise issue, most useful things  
are in papers, look at the references 
 
*   Ulrich L. Rohde, Ajay K. Poddar, Georg Böck  "The Design of Modern 
Microwave Oscillators for Wireless Applications ", John  Wiley & Sons, New 
York, NY, May, 2005, _ISBN  0-471-72342-8_ 
(https://en.wikipedia.org/wiki/Special:BookSources/0471723428) . 
*   George Vendelin, Anthony M. Pavio, Ulrich L.  Rohde " Microwave 
Circuit Design Using Linear and Nonlinear Techniques ", John  Wiley & Sons, New 
York, NY, May, 2005, _ISBN  0-471-41479-4_ 
(https://en.wikipedia.org/wiki/Special:BookSources/0471414794) . 
*   Ulrich L. Rohde, Anisha M. Apte 
http://ieeexplore.ieee.org/document/7506417/ Everything You Always Wanted to 
Know  About Colpitts Oscillators 
[Applications Note] 
*   Anisha M. Apte; Ajay K. Poddar; Ulrich L.  Rohde; Enrico Rubiola, 
Colpitts oscillator: A new criterion of energy saving  for high performance 
signal sources 2016 IEEE International Frequency Control  Symposium (IFCS)
 
Not because my name is  there but we tried to list ALL relevant literature, 
also 
 
https://www.amazon.com/Design-Crystal-Other-Harmonic-Oscillators/dp/04710881
96
 
is useful and look at 
 
http://ieeexplore.ieee.org/Xplore/home.jsp   .
 
In the last 10 years Dr. Poddar and I have  done the most oscillator and 
phase noise work..Look us up at Xplore
 
73 de Ulrich 
 
 
In a message dated 10/29/2016 3:38:34 P.M. Eastern Daylight Time,  
scott.j.sto...@gmail.com writes:

I found Frerking's "Crystal Oscillator Design and Temperature  
Compensation" to be a fruitful read. It's free on the archive, 
https://archive.org/details/CrystalOscillatorDesignTemperatureCompensation  .  


Are there any recommendations for one or more book(s) that are definitely  
worth skimming through, or reading?


On Sat, Oct 29, 2016 at 3:12 PM, KA2WEU--- via  time-nuts 
<_time-nuts@febo.com_ (mailto:time-nuts@febo.com) > wrote:

Some  useful literature

_https://en.wikipedia.org/wiki/https://en._ 
(https://en.wikipedia.org/wiki/Phase_noise) 


_https://en.wikipedia.org/wiki/https://en.wikipedi_ 
(https://en.wikipedia.org/wiki/Colpitts_oscillator) 

Some  links seem not to work   73 de  Ulrich

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Re: [time-nuts] WWVB software for PC

[Hal Murray]

> Any freeware out there to decode WWVB or any of the other standards out
> there? Using an audio card and pc?

The low cost WWVB receivers put out an on/off signal which can be wired up to 
a modem control signal.

Many many years ago, I found some software that decoded that.  Or tried to.  
I never got it working well enough to be interesting.  Too much EMI or 
something like that.

I'm pretty sure it was setup to feed ntpd via SHM, but I never got that far.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] IRIG-B for OS X

[Chris Albertson]

Generator?   I know there is a decoder in NTP.I thought the only
generator was the WWVB timecode generator in the "test" directory.In
any case NTP work the same all the various platforms as I think there is
only one source distribution.

I use OS X too.  I find the best way to locate software like this is to
hunt for the Linux version.  Then if it runs on Linux it usually can be
made to run on OS X

On Sat, Oct 29, 2016 at 1:01 PM, bownes  wrote:

>
> Has anyone seen an IRIG-B generator for OS X sound port?
>
> I know there is one for the PC in NTP, but thought I would ask before
> diving in to that asp pit.
>
> Bob
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Redondo Beach, California
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Re: [time-nuts] WWV receivers?

[Chris Albertson]

There is zero jitter through the SDR software because you can always buffer
the output and then reclock it on output and all you have to deal with is a
known fixed delay.  If the samples are clocked in accurately that is all
you need.

Some audio interfaces have can have very good timing and run off an
external reference oscillator.  But those are typically found in
professional studios.  (Some studios have coax or fiber frequency
distribution.) But The typical home studio audio interface that sells for
under $200 uses a four pin  oscillator.

The bigger question is propagation.



On Sat, Oct 29, 2016 at 12:07 PM, Attila Kinali  wrote:

> On Sat, 29 Oct 2016 09:35:25 -0700
> jimlux  wrote:
>
> > > Should not be too high. If Jeff Sherman's and Robert Jörden's paper[1]
> > > is any indication, then the jitter should be dominated by the jitter
> > > of the ADC and its reference oscillator. So sub-ps, order of 100fs
> jitter
> > > should be possible with proper design. Long term drift is another issue
> > > and I have not completely figured out what are the contributors there.
> > > Temperature stabilizing for sure helps, but it doesn't seem to be the
> > > only effect.
> >
> >
> > Well, that's "jitter in the original samples" which can be very low, as
> > you describe. But I would interpret the original question as "jitter
> > *through* an SDR" which implies that we're looking at the timing of
> > output vs input.
>
> Oh.. yes...The whole latency into the PC is a whole different game.
> I don't know the numbers for SDR, but for soundcards that delay jitter
> is usually in the couple 100µs range, Ie way lower than most people
> would notice. But this is only true if the OS reports the buffer sizes
> correctly. On Linux that means no pulseaudio as it is known to mess up
> the buffer reporting completely, to the point where it was off by 10's of
> ms.
>
> I don't know what the numbers under windows are, but as I have never heard
> of any problems there it might just work correctly out of the box.
>
> Those I know who do precsision timing with SDR usually use the timestamping
> facilities on the SDR hardware and process those timestamps within
> GnuRadio.
>
> Attila Kinali
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
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Redondo Beach, California
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Re: [time-nuts] WWVB software for PC

[Chris Albertson]

Yes,  you may even already have such software installed on your computer.
It comes with the standard NTP server installation.   If you modify the NTP
config file to use a WWVB reference clock then it will load the driver and
listen on an audio interface

On Sat, Oct 29, 2016 at 12:32 PM, Chris Arnold via time-nuts <
time-nuts@febo.com> wrote:

> Any freeware out there to decode WWVB or any of the other standards out
> there? Using an audio card and pc?
> I've tried RadioClock and Clock that comes with Multipsk, but want to see
> whats else is out there. Not looking for anything to set the PC clock, just
> a mild curiosity of whats happening, signal quality or other info its
> putting out.
>
>
> N3IZN
>
>
>
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-- 

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Redondo Beach, California
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[time-nuts] IRIG-B for OS X

[bownes]

Has anyone seen an IRIG-B generator for OS X sound port?

I know there is one for the PC in NTP, but thought I would ask before diving in 
to that asp pit. 

Bob
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Re: [time-nuts] our favorite topics

[Scott Stobbe]

I found Frerking's "Crystal Oscillator Design and Temperature Compensation"
to be a fruitful read. It's free on the archive,
https://archive.org/details/CrystalOscillatorDesignTemperatureCompensation .

Are there any recommendations for one or more book(s) that are definitely
worth skimming through, or reading?

On Sat, Oct 29, 2016 at 3:12 PM, KA2WEU--- via time-nuts  wrote:

> Some useful literature
>
> https://en.wikipedia.org/wiki/Phase_noise
>
>
> https://en.wikipedia.org/wiki/Colpitts_oscillator
>
> Some links seem not to work   73 de Ulrich
>
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[time-nuts] WWVB software for PC

[Chris Arnold via time-nuts]

Any freeware out there to decode WWVB or any of the other standards out there? 
Using an audio card and pc?
I've tried RadioClock and Clock that comes with Multipsk, but want to see whats 
else is out there. Not looking for anything to set the PC clock, just a mild 
curiosity of whats happening, signal quality or other info its putting out.


N3IZN



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Re: [time-nuts] WWV receivers?

[Nick Sayer via time-nuts]

No, no, no.

The single chip in this case is an AFSK decoder. You still have to have an 
ordinary HF AM radio.

> On Oct 29, 2016, at 11:21 AM, Chris Albertson  
> wrote:
> 
> Are you sure the single chip receiver is not itself an SDR?  Maybe using a 
> little 8-bit uP inside?  I don't know.
> 
> In any case the jitter on the SDR depends on the sample rate clock.  If you 
> use a decent audio interface the clocks are not bad.  A little 4-pin crystal 
> oscillator controls the sampling.   Compared to the propagation delay the 
> quality of that crystal is a not a big deal.   
> 
> On Fri, Oct 28, 2016 at 10:36 PM, Nick Sayer via time-nuts 
> > wrote:
> That single-chip version is going to have a *LOT* less (and less variable) 
> latency than an SDR.
> 
> > On Oct 27, 2016, at 12:20 AM, Poul-Henning Kamp  > > wrote:
> >
> > 
> > In message <5a002554-8d90-4c75-95da-21db45d61...@kfu.com 
> > >, Nick Sayer via time-
> > nuts writes:
> >
> >> If you’re in North America, a CHU receiver is a lot easier to make
> >> than WWV/WWVH. The CHU timecode is just BEL 103 AFSK at 300 baud -
> >> it was a one-chip solution 20 years ago when I made one in college.
> >
> > We have CPUs and sounds-cards these days...
> >
> > Also: The KiwiSDR is nearly perfect hardware, no matter which VLF/HF
> > station you want:  You can track GPS and four (possibly 8) VLF/HF
> > stations at the same time.
> >
> > --
> > Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> > p...@freebsd.org | TCP/IP since RFC 956
> > FreeBSD committer   | BSD since 4.3-tahoe
> > Never attribute to malice what can adequately be explained by incompetence.
> 
> ___
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> 
> and follow the instructions there.
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California

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Re: [time-nuts] hp 5065A

[timeok]

   Hi John,
   you can visit the pages:
   http://www.timeok.it/hp5065a-corner-3/
   regards,
   Luciano
   timeok


   From "time-nuts" time-nuts-boun...@febo.com
   To "Discussion of precise time and frequency measurement" time-nuts@febo.com
   Cc
   Date Sat, 29 Oct 2016 10:47:55 -0700
   Subject Re: [time-nuts] hp 5065A
   On 10/29/2016 9:42 AM, John Ponsonby wrote:
   > Gentlemen,
   > I am interested in getting an old hp 5065A Rubidium frequency standard 
working again. I recall that if one of these units is left not running for a 
long time that the rubidium atoms get adsorbed onto the glass of the cell and 
filter.
   John, the procedure for that is on page 3-1 and 2 of the manual, but it
   may not be necessary. Lots has been published about these and I'm sure
   a Google search will turn them up, in particular there's an Italian
   authored pdf from, I think, a member of this group. There are some
   electrolytic caps that will need to be checked and replaced where necessary.

   Having said that mine came back to life after being in dusty storage for
   about ten years and all it needed was a good clean...

   Dan
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[time-nuts] our favorite topics

[KA2WEU--- via time-nuts]

Some useful literature
   
https://en.wikipedia.org/wiki/Phase_noise
 
 
https://en.wikipedia.org/wiki/Colpitts_oscillator
 
Some links seem not to work   73 de Ulrich 
 
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Re: [time-nuts] WWV receivers?

[Attila Kinali]

On Sat, 29 Oct 2016 09:35:25 -0700
jimlux  wrote:

> > Should not be too high. If Jeff Sherman's and Robert Jörden's paper[1]
> > is any indication, then the jitter should be dominated by the jitter
> > of the ADC and its reference oscillator. So sub-ps, order of 100fs jitter
> > should be possible with proper design. Long term drift is another issue
> > and I have not completely figured out what are the contributors there.
> > Temperature stabilizing for sure helps, but it doesn't seem to be the
> > only effect.
> 
> 
> Well, that's "jitter in the original samples" which can be very low, as 
> you describe. But I would interpret the original question as "jitter 
> *through* an SDR" which implies that we're looking at the timing of 
> output vs input.

Oh.. yes...The whole latency into the PC is a whole different game.
I don't know the numbers for SDR, but for soundcards that delay jitter
is usually in the couple 100µs range, Ie way lower than most people
would notice. But this is only true if the OS reports the buffer sizes
correctly. On Linux that means no pulseaudio as it is known to mess up
the buffer reporting completely, to the point where it was off by 10's of ms.

I don't know what the numbers under windows are, but as I have never heard
of any problems there it might just work correctly out of the box.

Those I know who do precsision timing with SDR usually use the timestamping
facilities on the SDR hardware and process those timestamps within GnuRadio.

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] WWV receivers?

[Chris Albertson]

Are you sure the single chip receiver is not itself an SDR?  Maybe using a
little 8-bit uP inside?  I don't know.

In any case the jitter on the SDR depends on the sample rate clock.  If you
use a decent audio interface the clocks are not bad.  A little 4-pin
crystal oscillator controls the sampling.   Compared to the propagation
delay the quality of that crystal is a not a big deal.

On Fri, Oct 28, 2016 at 10:36 PM, Nick Sayer via time-nuts <
time-nuts@febo.com> wrote:

> That single-chip version is going to have a *LOT* less (and less variable)
> latency than an SDR.
>
> > On Oct 27, 2016, at 12:20 AM, Poul-Henning Kamp 
> wrote:
> >
> > 
> > In message <5a002554-8d90-4c75-95da-21db45d61...@kfu.com>, Nick Sayer
> via time-
> > nuts writes:
> >
> >> If you’re in North America, a CHU receiver is a lot easier to make
> >> than WWV/WWVH. The CHU timecode is just BEL 103 AFSK at 300 baud -
> >> it was a one-chip solution 20 years ago when I made one in college.
> >
> > We have CPUs and sounds-cards these days...
> >
> > Also: The KiwiSDR is nearly perfect hardware, no matter which VLF/HF
> > station you want:  You can track GPS and four (possibly 8) VLF/HF
> > stations at the same time.
> >
> > --
> > Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> > p...@freebsd.org | TCP/IP since RFC 956
> > FreeBSD committer   | BSD since 4.3-tahoe
> > Never attribute to malice what can adequately be explained by
> incompetence.
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] hp 5065A

[Dan Rae]

On 10/29/2016 9:42 AM, John Ponsonby wrote:

Gentlemen,
I am interested in getting an old hp 5065A Rubidium frequency standard 
working again. I recall that if one of these units is left not running for a 
long time that the rubidium atoms get adsorbed onto the glass of the cell and 
filter.
John, the procedure for that is on page 3-1 and 2 of the manual, but it 
may not be necessary.  Lots has been published about these and I'm sure 
a Google search will turn them up, in particular there's an Italian 
authored pdf from, I think, a member of this group.  There are some 
electrolytic caps that will need to be checked and replaced where necessary.


Having said that mine came back to life after being in dusty storage for 
about ten years and all it needed was a good clean...


Dan
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[time-nuts] TNS-BUF Update

[John Ackermann N8UR]

We had enough interest in the TNS-BUF isolation amplifier project to go 
ahead with a production run.  Thanks!


The order has been placed with our contract manufacturer in Hungary and 
we expect the boards to arrive at the TAPR office in Texas around 
January 1, plus or minus shipping and customs delays.  It'll take a 
little while for the office to recover from New Year's Eve, so we expect 
to get all orders shipped by mid-January.


If you placed an order, you'll be getting an email from TAPR with 
further details. And of course if the schedule changes, I'll provide an 
update.


BTW -- depending on manufacturing yield, there may be a few extra 
assembled boards available, as well as some bare PCB.  I'll announce 
when we know for sure.


Thanks, all.

John
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[time-nuts] hp 5065A

[John Ponsonby]

Gentlemen,
I am interested in getting an old hp 5065A Rubidium frequency standard 
working again. I recall that if one of these units is left not running for a 
long time that the rubidium atoms get adsorbed onto the glass of the cell and 
filter. I recall long ago having a note as to how to get the rubidium off the 
surfaces again. It involved unsoldering some of the connections to the RVFR and 
connecting instead to a external DC supply for a week or so. I guess this was 
to heat the internals well above their usual working temperature. But I've 
forgotten the details, what current and voltage is required. One could 
obviously cause permanent damage by overdoing it. Does anybody know about this?
Regards
John P 
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Re: [time-nuts] WWV receivers?

[jimlux]

On 10/29/16 4:49 AM, Attila Kinali wrote:

On Fri, 28 Oct 2016 23:01:52 -0700
Hal Murray  wrote:


nsa...@kfu.com said:

That single-chip version is going to have a *LOT* less (and less variable)
latency than an SDR.


Latency isn't an issue as long as it is known so that you can correct for it.

Has anybody measured the jitter through SDR and/or tried to reduce it?  I'd
expect that even if you counted cycles and such there would still be jitter
from not being able to reproduce cache misses and interrupts.


Should not be too high. If Jeff Sherman's and Robert Jörden's paper[1]
is any indication, then the jitter should be dominated by the jitter
of the ADC and its reference oscillator. So sub-ps, order of 100fs jitter
should be possible with proper design. Long term drift is another issue
and I have not completely figured out what are the contributors there.
Temperature stabilizing for sure helps, but it doesn't seem to be the
only effect.



Well, that's "jitter in the original samples" which can be very low, as 
you describe. But I would interpret the original question as "jitter 
*through* an SDR" which implies that we're looking at the timing of 
output vs input.


Consider an SDR which receives a RF signal that's BPSK modulated, and 
puts out a stream of data bits on a wire (as opposed to dumping into a 
file or network connection)-  and you want to look at an eye diagram of 
the output.






Attila Kinali

[1] "Oscillator metrology with software defined radio",
by Jeff Sherman and Robert Jörden, 2016
http://dx.doi.org/10.1063/1.4950898
http://arxiv.org/abs/1605.03505




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Re: [time-nuts] Opening an Isotemp OCXO

[paul swed]

if its the yellow tantalum. then yes 39 uf at 10V.
S sort of surprised it didn't go nuclear on you.
Makes for a serious mess.
Regards
Paul
WB8TSL

On Sat, Oct 29, 2016 at 9:59 AM, Bob Camp  wrote:

> Hi
>
> If the OCXO was designed for a ~70 C upper end temperature spec, then a
> ~90C crystal
> would make sense.
>
> When you feed +12 into the oven control, you are increasing the effective
> gain of the control
> loop (it has more power). The cycling you see is the loop going into
> oscillation. It’s the same thing that happens if
> you put way to much insulation around an OCXO.
>
> I *hope* the 4 amps below is a typo. 20W into the beast is way to much.
> 0.4 A at 5V would be
> 2W. That is a fairly normal number for an OCXO like you have at room
> temperature.
>
> Bob
>
>
> > On Oct 29, 2016, at 9:51 AM, Peter Reilley 
> wrote:
> >
> > More information;
> >
> > I added a picture to the dropbox from my Flir IR camera.   The picture
> shows the copper block
> > that the crystal is attached to running at about 200 F.   In the IR shot
> the copper block is to the
> > right.In most of the regular pictures it is toward the bottom of the
> picture.This is with the
> > unit (minus the S30 chip) running on 5 volts for more than 10 hours.
>  Is that too hot?
> >
> > While running at 5 volts the current is constant at about 4. amps, no
> cycling.   At 12 volts
> > it cycled between .9 to .1 amps.   I would not expect cycling for the
> temperature control
> > of an OCXO.   I would expect a linear temperature control circuit.
> >
> > I looked at the tantalum capacitor on the bottom of the board.   The
> marking is 39-10.
> > Does that mean 39 uF and 10 volts?   If so then it must be a 5 volt
> unit.   The capacitor
> > did not explode at 12 volts.
> >
> > Dropbox link:
> > https://www.dropbox.com/sh/52e9d1rva9kpb3w/
> AABmbIj1aK7Zk2J9SNMmu-JAa?dl=0
> >
> > Pete.
> >
> > On 10/18/2016 9:11 AM, Peter Reilley wrote:
> >> I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at
> the MIT flea market.
> >> As expected it was dead.   It heats up as expected but looking at the
> output with a scope there
> >> is nothing.   However looking at the output with a spectrum analyzer I
> can see a faint 10 MHz
> >> signal.   It seems that the oscillator is running but the output
> circuitry is dead.   Reasonable
> >> assumption?
> >>
> >> Anyway, has anyone had any luck unsoldering the tin case without
> destroying it?
> >>
> >> Pete.
> >>
> >> ___
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Re: [time-nuts] WWV receivers?

[paul swed]

Good thread. Thanks for the clue on the kiwiSDR. I went to the sites and
lots of fun playing with the receivers. As an example hearing LORAN C in
the Asia region.
Certainly seems the receiver is pretty sensitive and capable. Went hunting
for various low frequency timing signals such as JJY and the submarine
crusher signals. All were heard.
I agree with Bobs comments that the signal at WWV range can be all over the
place and though seasonal effects can be a somewhat accounted for the
reality is, its still pretty random. The changes can occur slowly or
rapidly.
Regards
Paul
WB8TSL

On Sat, Oct 29, 2016 at 9:03 AM, Bob Camp  wrote:

> Hi
>
> Let’s see…. WWV (not WWVB) gets here via a variety of propagation
> mechanisms
> that vary over the day. According to NIST (who probably know :) that puts
> a random timing
> variation of ~1 ms on the signal. Since some modes get me a signal and
> others don’t, there
> is no real reason to assume it is random. It can easily be an offset that
> varies month to month.
>
> Net result, forget about the chip delays. The signal already has a bunch
> of built in variability
> that will swamp anything in the silicon.
>
> https://www.nist.gov/pml/time-and-frequency-division/nist-
> radio-broadcasts-frequently-asked-questions-faq
>
> Also in the same data is the fact that the “as transmitted” signal is good
> to 100 ns. That’s plenty good
> enough for the system as described. It also is a pretty modest number for
> a GPS timing module. One
> would guess that the number is a bit better than 100 ns (it is NIST after
> all). It also does not directly
> compare to the GPS number since there are UTC offset numbers there as
> well. Bottom line is that
> there inevitably *are* numbers like that buried in the system once you get
> past the 1 ms.
>
> Bob
>
> > On Oct 29, 2016, at 1:36 AM, Nick Sayer via time-nuts <
> time-nuts@febo.com> wrote:
> >
> > That single-chip version is going to have a *LOT* less (and less
> variable) latency than an SDR.
> >
> >> On Oct 27, 2016, at 12:20 AM, Poul-Henning Kamp 
> wrote:
> >>
> >> 
> >> In message <5a002554-8d90-4c75-95da-21db45d61...@kfu.com>, Nick Sayer
> via time-
> >> nuts writes:
> >>
> >>> If you’re in North America, a CHU receiver is a lot easier to make
> >>> than WWV/WWVH. The CHU timecode is just BEL 103 AFSK at 300 baud -
> >>> it was a one-chip solution 20 years ago when I made one in college.
> >>
> >> We have CPUs and sounds-cards these days...
> >>
> >> Also: The KiwiSDR is nearly perfect hardware, no matter which VLF/HF
> >> station you want:  You can track GPS and four (possibly 8) VLF/HF
> >> stations at the same time.
> >>
> >> --
> >> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> >> p...@freebsd.org | TCP/IP since RFC 956
> >> FreeBSD committer   | BSD since 4.3-tahoe
> >> Never attribute to malice what can adequately be explained by
> incompetence.
> >
> > ___
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> mailman/listinfo/time-nuts
> > and follow the instructions there.
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Re: [time-nuts] Opening an Isotemp OCXO

[Bob Camp]

Hi

If the OCXO was designed for a ~70 C upper end temperature spec, then a ~90C 
crystal
would make sense. 

When you feed +12 into the oven control, you are increasing the effective gain 
of the control
loop (it has more power). The cycling you see is the loop going into 
oscillation. It’s the same thing that happens if
you put way to much insulation around an OCXO. 

I *hope* the 4 amps below is a typo. 20W into the beast is way to much. 0.4 A 
at 5V would be
2W. That is a fairly normal number for an OCXO like you have at room 
temperature. 

Bob


> On Oct 29, 2016, at 9:51 AM, Peter Reilley  wrote:
> 
> More information;
> 
> I added a picture to the dropbox from my Flir IR camera.   The picture shows 
> the copper block
> that the crystal is attached to running at about 200 F.   In the IR shot the 
> copper block is to the
> right.In most of the regular pictures it is toward the bottom of the 
> picture.This is with the
> unit (minus the S30 chip) running on 5 volts for more than 10 hours.   Is 
> that too hot?
> 
> While running at 5 volts the current is constant at about 4. amps, no 
> cycling.   At 12 volts
> it cycled between .9 to .1 amps.   I would not expect cycling for the 
> temperature control
> of an OCXO.   I would expect a linear temperature control circuit.
> 
> I looked at the tantalum capacitor on the bottom of the board.   The marking 
> is 39-10.
> Does that mean 39 uF and 10 volts?   If so then it must be a 5 volt unit.   
> The capacitor
> did not explode at 12 volts.
> 
> Dropbox link:
> https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?dl=0
> 
> Pete.
> 
> On 10/18/2016 9:11 AM, Peter Reilley wrote:
>> I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at the MIT 
>> flea market.
>> As expected it was dead.   It heats up as expected but looking at the output 
>> with a scope there
>> is nothing.   However looking at the output with a spectrum analyzer I can 
>> see a faint 10 MHz
>> signal.   It seems that the oscillator is running but the output circuitry 
>> is dead.   Reasonable
>> assumption?
>> 
>> Anyway, has anyone had any luck unsoldering the tin case without destroying 
>> it?
>> 
>> Pete.
>> 
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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

More information;

I added a picture to the dropbox from my Flir IR camera.   The picture 
shows the copper block
that the crystal is attached to running at about 200 F.   In the IR shot 
the copper block is to the
right.In most of the regular pictures it is toward the bottom of the 
picture.This is with the
unit (minus the S30 chip) running on 5 volts for more than 10 hours.   
Is that too hot?


While running at 5 volts the current is constant at about 4. amps, no 
cycling.   At 12 volts
it cycled between .9 to .1 amps.   I would not expect cycling for the 
temperature control

of an OCXO.   I would expect a linear temperature control circuit.

I looked at the tantalum capacitor on the bottom of the board.   The 
marking is 39-10.
Does that mean 39 uF and 10 volts?   If so then it must be a 5 volt 
unit.   The capacitor

did not explode at 12 volts.

Dropbox link:
https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?dl=0

Pete.

On 10/18/2016 9:11 AM, Peter Reilley wrote:
I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at 
the MIT flea market.
As expected it was dead.   It heats up as expected but looking at the 
output with a scope there
is nothing.   However looking at the output with a spectrum analyzer I 
can see a faint 10 MHz
signal.   It seems that the oscillator is running but the output 
circuitry is dead.   Reasonable

assumption?

Anyway, has anyone had any luck unsoldering the tin case without 
destroying it?


Pete.

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[time-nuts] What would be the proper equipment and procedure?

[William H. Fite]

Bill, it isn't quite so simple as that. While handling and ingestion of
metallic mercury is ordinarily benign, inhalation of mercury vapor is not.
The vapor pressure of metallic mercury is quite low but even very modest
concentrations, which can readily occur at room temperature, can exhibit
significant toxicity when inhaled. As odd as it sounds, metallic mercury is
slightly soluble in water and aqueous solutions. Mercury in solution is
readily absorbed and quite toxic.

Organic mercury compounds (dimethylmercury, monomethylmercury, others) are
profoundly and generally irreversibly neurotoxic. Cf. Karen Wetterhahn,
Dartmouth College, 1997; Minamata Disease, Japan, 1956. Inorganic mercury
compounds exhibit a broad range of toxicities and some are corrosive.

I'm like you and your dad in that I played with mercury as a child. Mother
once gave me a pound of it for my birthday (yes, weird family). I, too,
have lived for many years since then. However, the fact that exposure to
even very small amounts of mercury vapor can result in subclinical neuronal
loss may explain why neither you nor I have ever been handed a medal by the
King of Sweden

You're correct that people often overreact to the risk of mercury toxicity.
Many years ago, when I was the director of a large trauma center, a woman
came tearing in at midnight, accompanied by her husband and eight year old
son. Between hysterical sobs, she explained that she had found the boy
playing with a tiny blob of mercury. "Do something!", she screeched. "He's
going to die of Manny Mota disease." A resident helpfully remarked, "So
long as he sticks to the minor leagues, he should be fine." This caused her
husband to laugh aloud and doubtless provoked a domestic discussion later.

Moon suits are not necessary for the cleanup of modest amounts of mercury
but the suggestion that mercury in metallic form is a benign substance is
not correct. It should be handled with reasonable laboratory precautions
and kept out of the hands of children and mindless dolts. Unwise to use it
to determine gastrointestinal transit time, too, though that is a novel
idea.

Other Bill



On Saturday, October 29, 2016, Bill Hawkins  wrote:

> Ah, you might not have meant that for this list. You are a man of many
> talents.
>
> Dimethyl mercury has given elemental mercury a bad name it doesn't
> deserve. As a youth, I used it to turn pennies into silvery dimes.
> Father said he'd ingested a teaspoon to see how fast it would go through
> him. In his day, beryllium pliers were used around explosives because
> they were non-sparking. We both lived many years afterwards. People who
> don't understand the difference between elements and compounds insist
> that cleaning up after a broken mercury thermometer be done wearing moon
> suits. So it goes - as time goes by.
>
> Bill Hawkins
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark
> Sims
> Sent: Friday, October 28, 2016 10:26 PM
> To: time-nuts@febo.com
> Subject: [time-nuts] What would be the proper equipment and procedure?
>
> I don't know if it the proper way but I used a very nice fume hood.
> Measured the metals (high purity),  melted them in a quartz crucible,
> stirred with a quartz rod,  and cast it in a ceramic block with a spiral
> pattern machined into it with a ball mill. You don't want to contaminate
> the mixture with other metals, etc.
>
> That "Things I Won't Work With" article was about dimethyl cadmium, not
> metallic cadmium.  Reall Nasty Stuff.  Metallic cadmium and cadmium
> plating has been used for ages without killing too many people.  It's
> not something to take lightly, but I've had the pleasure of working
> around far worse things.
>
> For even more extreme nastiness check out dimethyl mercury... one drop,
> goes through rubber gloves like they aren't there,  sure-fire rather
> horrible death.   Derek Lowe's "Things I Won't Work With" series is some
> of the best reading out there...  Unfortunately,  I don't think that he
> is still doing them.  His old web site has disappeared.
> ___
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Re: [time-nuts] WWV receivers?

[Bob Camp]

Hi

Let’s see…. WWV (not WWVB) gets here via a variety of propagation mechanisms 
that vary over the day. According to NIST (who probably know :) that puts a 
random timing
variation of ~1 ms on the signal. Since some modes get me a signal and others 
don’t, there
is no real reason to assume it is random. It can easily be an offset that 
varies month to month. 

Net result, forget about the chip delays. The signal already has a bunch of 
built in variability
that will swamp anything in the silicon. 

https://www.nist.gov/pml/time-and-frequency-division/nist-radio-broadcasts-frequently-asked-questions-faq

Also in the same data is the fact that the “as transmitted” signal is good to 
100 ns. That’s plenty good
enough for the system as described. It also is a pretty modest number for a GPS 
timing module. One
would guess that the number is a bit better than 100 ns (it is NIST after all). 
It also does not directly
compare to the GPS number since there are UTC offset numbers there as well. 
Bottom line is that
there inevitably *are* numbers like that buried in the system once you get past 
the 1 ms. 

Bob

> On Oct 29, 2016, at 1:36 AM, Nick Sayer via time-nuts  
> wrote:
> 
> That single-chip version is going to have a *LOT* less (and less variable) 
> latency than an SDR.
> 
>> On Oct 27, 2016, at 12:20 AM, Poul-Henning Kamp  wrote:
>> 
>> 
>> In message <5a002554-8d90-4c75-95da-21db45d61...@kfu.com>, Nick Sayer via 
>> time-
>> nuts writes:
>> 
>>> If you’re in North America, a CHU receiver is a lot easier to make
>>> than WWV/WWVH. The CHU timecode is just BEL 103 AFSK at 300 baud -
>>> it was a one-chip solution 20 years ago when I made one in college.
>> 
>> We have CPUs and sounds-cards these days...
>> 
>> Also: The KiwiSDR is nearly perfect hardware, no matter which VLF/HF
>> station you want:  You can track GPS and four (possibly 8) VLF/HF
>> stations at the same time.
>> 
>> -- 
>> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>> p...@freebsd.org | TCP/IP since RFC 956
>> FreeBSD committer   | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
> 
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Re: [time-nuts] WWV receivers?

[Poul-Henning Kamp]

In message <20161029134952.e60a2182e1f53844ec50b...@kinali.ch>, Attila Kinali 
writes:

>> nsa...@kfu.com said:
>> > That single-chip version is going to have a *LOT* less (and less variable)
>> > latency than an SDR. 
>> 
>> Latency isn't an issue as long as it is known so that you can correct for it.
>> 
>> Has anybody measured the jitter through SDR and/or tried to reduce it?  I'd 
>> expect that even if you counted cycles and such there would still be jitter 
>> from not being able to reproduce cache misses and interrupts.
>
>Should not be too high.

It should be nonexistent.

The sensible way to do SDR-timing, is to capture a signal from the disciplined
oscillator with the ADC samples, so that their precise timing relationship is
firmly bolted down.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] WWV receivers?

[Attila Kinali]

On Fri, 28 Oct 2016 23:01:52 -0700
Hal Murray  wrote:

> nsa...@kfu.com said:
> > That single-chip version is going to have a *LOT* less (and less variable)
> > latency than an SDR. 
> 
> Latency isn't an issue as long as it is known so that you can correct for it.
> 
> Has anybody measured the jitter through SDR and/or tried to reduce it?  I'd 
> expect that even if you counted cycles and such there would still be jitter 
> from not being able to reproduce cache misses and interrupts.

Should not be too high. If Jeff Sherman's and Robert Jörden's paper[1]
is any indication, then the jitter should be dominated by the jitter
of the ADC and its reference oscillator. So sub-ps, order of 100fs jitter
should be possible with proper design. Long term drift is another issue
and I have not completely figured out what are the contributors there.
Temperature stabilizing for sure helps, but it doesn't seem to be the
only effect.


Attila Kinali

[1] "Oscillator metrology with software defined radio",
by Jeff Sherman and Robert Jörden, 2016
http://dx.doi.org/10.1063/1.4950898
http://arxiv.org/abs/1605.03505


-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] What would be the proper equipment and procedure?

[David]

But I got my question answered anyway. :)

On Sat, 29 Oct 2016 05:29:26 +, you wrote:

>Yep, should have gone to volt-nuts.   Recent changes Microsoft has been doing 
>to Outlook, etc have been causing all sorts of fun gltches.  One being not 
>actually taking copy-pastes of addresses and/or subject lines.  Another being 
>sorting emails into dark and crusty corners of ancient folders...   We were 
>talking about the hazards of making cadmium-tin low thermal EMF solder...
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Re: [time-nuts] WWV receivers?

[Hal Murray]

nsa...@kfu.com said:
> That single-chip version is going to have a *LOT* less (and less variable)
> latency than an SDR. 

Latency isn't an issue as long as it is known so that you can correct for it.

Has anybody measured the jitter through SDR and/or tried to reduce it?  I'd 
expect that even if you counted cycles and such there would still be jitter 
from not being able to reproduce cache misses and interrupts.

-- 
These are my opinions.  I hate spam.



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